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Impact of PCC Pavement Structural Rolling
Resistance on Vehicle Fuel Economy
Danilo Balzarini, Imen Zaabar, and Karim Chatti
Department of Civil & Environmental Engineering
Michigan State University
This study was conducted in collaboration with
Dr. John Harvey (University of California, Davis)
and Dr. Erdem Coleri (Oregon State University).
The authors would like to acknowledge the
financial support of the California Department
of Transportation.
Acknowledgements
2
Introduction
Objective
Approach
Calculation of the fuel consumption due to the structural rolling resistance
Results
Conclusion
Outline
3
Factors Affecting Fuel Consumption
Vehicle
Thermodynamic efficiency of the engine
Aerodynamics
Weight
Technological characteristics of the tire:
• Inflation Pressure
• Temperature
• Design, materials, dimensions
Pavement
Geometry
Surface characteristics
Structural behavior of the pavement 4
Objective
Evaluate the effects of concrete pavement
structural characteristics on rolling resistance
(SRR) and fuel consumption using a mechanistic
approach
5
Approach
6
Backcalculation
Eliminate the noise from the FWD time histories
Use FFT algorithm to decompose the deflection
signal of each sensor into a series of harmonic
motions
Use a closed form solution for the dynamic
backcalculation of the effective k and c values
for the base/subgrade
Use the best fit method to get the static k value
and the elastic modulus of the concrete slab
Compare the static and dynamic k values
7
Dynamic Backcalculation(Chatti, 1992)
2
22
00
ImRe
Im)Im(Re)Re(
AA
AA
UdAUdA
UdAPUdAP
k
22
00
ImRe
Re)Im(Im)Re(1
AA
AA
UdAUdA
UdAPUdAP
c
8
FWD Deflection Time Histories
9
DYNASLAB (Chatti, 1992)
2D Dynamic FE model with moving loads
Elastic slabs on damped Winkler foundation
Load transfer across joints modeled by a Kelvin-
Voigt model (vertical spring KAGG and dashpot
CAGG in parallel)10
Load Transfer Efficiency
Sensitivity analysis to correlate KAGG and CAGG tothe LTE of the joints
1(%) 100i
i
LTE
LTE sensitive to KAGG, not sensitive to CAGG
Even when LTE=100% joints have an impact onthe pavement response
11
Deflection as Seen by a Moving Vehicle
12
Slope as Seen by a Moving Vehicle
13
Front wheels of
Tandem axle
Rear wheels of
Tandem axle
Vehicle Energy Loss
Assumptions:
quasi-static regime
non-dissipative tires
To take into account the dependency of the slope
on time and on the location of the load, the slab is
divided into m intervals of length Δx
( , , , )str
RR
S
dw x y z tP p dS
dt
1 1
( , )n mj j
RR i i
i j
dw x tW p S x
dx
14
1000[ / ]diss RRW MJ km W
L
Calculation of Fuel Consumption
Fuel consumption due to
structural rolling resistance
Percent fuel
consumption excess
(due to SRR)
dissRR
b
WFuel
Type of engine b [MJ/L]
Gasoline 10.5
Diesel 16
100 100dissRRexcess
C b C
WFuelFuel
Fuel Fuel
b is the calorific value of
the fuel.
15
Pavement Sections
16
Vehicle Characteristics and Positions
Vehicle Class
Vehicle Characteristics
Number of axles
Number of tires
Load per Axle[kN]
Load per Tire [kN]
Medium Car 2 4 7.15 3.58
SUV 2 4 12.25 6.13
Loaded Truck 1 4 151.41 37.85
17
Excess Fuel Consumption Results – Truck
Tandem Axle
18
Excess Fuel Consumption Results - SUV
19
Excess Fuel Consumption Results - Car
20
Contribution of Rolling Resistance to
Fuel Consumption
FC [mL/km] (using NCHRP720 model)
% FC due to SRREdge Loading
% FC due to SRROffset Loading
50 km/h 100 km/h 50 km/h 100 km/h 50 km/h 100 km/h
Medium Car 70.0 95.6 0.002 0.002 0.001 0.002
SUV 78.7 120.9 0.004 0.006 0.003 0.004
Loaded Truck 273.4 551.7 0.072 0.081 0.064 0.072
SRR contribution to FC is less than 0.1%21
Conclusion
The excess fuel consumption of a vehicle travelling on
concrete pavements due to the SRR is a very small quantity:
less than 0.1% of the total fuel consumption of the truck.
While this excess fuel consumption due to the structural
rolling resistance is very small, it has been shown that:
Increasing the speed increases the fuel consumption
due to SRR.
The fuel consumption due to SRR increases as the
wheel is closer to the slab edge.
A stronger foundation (base and subgrade) reduces
the fuel consumption due to SRR. 22
Future Studies
Study the effect of shoulders/adjacent lanes and
LTE less than 100%
Consider the curling and warping effects
Compare the results with simulations on asphalt
and composite pavements
Thank you for your attention!23
Questions?
24